In terms of so-called “October Surprises” that might affect the election, the New Jersey Supreme Court ruling that opens the door to gay marriage certainly ranks below the congressional page scandal involving former Florida Rep. Mark Foley. But the decision could be a welcome boost for a White House and congressional Republicans worried about firing up the conservative base of their party.

Only Tuesday, Bush aides brought in a few dozen conservative radio talk show hosts to broadcast from the White House, where top officials such as Dick Cheney and Karl Rove tried to get them fired up about the importance of returning Republican majorities to Congress. And while G.O.P. leaders have been warning about high taxes and weakened national security if Democrats were to regain control of Congress, Republicans can now emphasize their differences with Democrats on an issue Christian conservatives are particularly passionate about. Most congressional Democrats voted against a constitutional amendment to ban gay marriage earlier this year. “It’s going to remind people this issue is paramount,” says the Rev. Louis Sheldon, who runs a conservative group called the Traditional Values Coalition.

Firing up the base is one thing, however. The open question is how much that impact will be felt in key races around the country. In New Jersey, Democratic incumbent Bob Menendez and Republican Tom Kean, who are both against gay marriage but for civil unions, are in a virtual tie in a crucial contest, and a Kean victory would almost certainly mean Republicans retained control of the Senate. But a Rutgers-Eagleton poll in June found 50% of people in the state favored gay marriage, while 44% opposed. And New Jersey is heavily Democratic, so it’s hard to see this decision putting Kean over the top.

What Republicans are hoping is that they can use the issue of gay marriage and the ruling to motivate conservatives in key states like Tennessee, Missouri and Virginia, where Republicans are in danger of losing Senate seats. Polls this year have shown small but measurable drop-offs in enthusiasm from Christian conservatives, and there’s some worry about whether they will stay home on Election Day, particularly after the Foley scandal, which some conservative leaders blamed on congressional Republicans for being too afraid to take action against Foley earlier because it might be perceived as anti-gay.

Measures to ban gay marriage are on the ballot in nine states, including Virginia and Tennessee, and conservative activists will point to the New Jersey decision as a reason people in those states should go to the polls, even if they’re dissatisfied with how the Republican majority has run the country. If that message resonates, the same people celebrating the New Jersey decision could be having mixed feelings about it come Election Day.